Selectively disable rubber banding on mac.

Source/web/WebInputEventFactoryMac.mm

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2006-2009 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 949 matching lines @@
 {
     if (![event respondsToSelector:@selector(momentumPhase)])
         return WebMouseWheelEvent::PhaseNone;
 
     NSEventPhase eventMomentumPhase = [event momentumPhase];
     return phaseForNSEventPhase(eventMomentumPhase);
 }
 
 WebMouseWheelEvent WebInputEventFactory::mouseWheelEvent(NSEvent* event, NSView* view)
 {
+    return mouseWheelEvent(event, view, true, true);
+}
+
+WebMouseWheelEvent WebInputEventFactory::mouseWheelEvent(NSEvent* event, NSView* view, bool canRubberbandLeft, bool canRubberbandRight)
+{
     WebMouseWheelEvent result;
 
     result.type = WebInputEvent::MouseWheel;
     result.button = WebMouseEvent::ButtonNone;
 
     result.modifiers = modifiersFromEvent(event);
 
     setWebEventLocationFromEventInView(&result, event, view);
 
+    result.canRubberbandLeft = canRubberbandLeft;
+    result.canRubberbandRight = canRubberbandRight;
+
     // Of Mice and Men
     // ---------------
     //
     // There are three types of scroll data available on a scroll wheel CGEvent.
     // Apple's documentation ([1]) is rather vague in their differences, and not
     // terribly helpful in deciding which to use. This is what's really going on.
     //
     // First, these events behave very differently depending on whether a standard
     // wheel mouse is used (one that scrolls in discrete units) or a
     // trackpad/Mighty Mouse is used (which both provide continuous scrolling).
@@ skipping 148 matching lines @@
         break;
     default:
         ASSERT_NOT_REACHED();
         result.type = WebInputEvent::Undefined;
     }
 
     return result;
 }
 
 } // namespace blink